Relativistic corrections become necessary when the expression for the kinetic energy \(\frac { 1 }{ 2 } m{ v }^{ 2 }\) becomes comparable with \(m{ c }^{ 2 }\) where m is the mass of the particle.At what de-Broglie wavelength will relativistic corrections become important for an electron?

1

(a)

\(\lambda =10nm\)

(b)

\(\lambda ={ 10 }^{ -1 }nm\)

(c)

\(\lambda ={ 10 }^{ -4 }nm\)

(d)

\(\lambda ={ 10 }^{ -6 }nm\)

The work function of lithium and copper are 2.3eV and 4.0eV respectively. Which of these metals will be useful for the photoelectric cell working with visible light? Explain.

1

(a)

Lithium, because its work function is less than the energy of the visible light photons.

It is harder to remove a free electron from copper than from sodium. Which has higher work function?

1

(a)

The work function of copper is higher than that of sodium.

An electron and photon possessing same K.E. Which one will have greater wavelength?